1. Field of the Invention
The present invention relates to an operation switching mechanism and an endoscope including a long member that transmits a force for operating an operating section.
2. Description of the Related Art
In recent years, endoscopes have been widely used in a medical field and an industrial field. With the endoscope used in the medical field, by inserting an elongated insertion section into a body cavity serving as a subject, it is possible to observe an organ in the body cavity with an optical system included in the insertion section and perform various kinds of treatment using, according to necessity, a treatment instrument inserted into an insert-through channel for the treatment instrument included in the endoscope.
With the endoscope used in the industrial field, by inserting an elongated insertion section of the endoscope into an object such as a jet engine or a pipe in a factory, it is possible to perform observation and inspection of scratches, corrosions, and the like of a site to be examined in the object with an optical system included in the insertion section.
A configuration is well known in which it is possible to change an observation magnification and a depth of field of a subject by reciprocatingly moving, using an operation switching mechanism, among optical members configuring an optical system provided in an insertion section of the endoscope, a zoom lens, which is an operating section, along an optical axis direction of the optical system.
More specifically, a configuration in which a known linear switch is used as the operation switching mechanism is well known. In the linear switch, a shape memory alloy for expanding to bias a zoom-lens holding frame, which holds a zoom lens, forward in an optical axis direction in a non-energized state and contracting to move the zoom-lens holding frame backward in the optical axis direction in an energized state is connected to the zoom-lens holding frame, whereby the linear switch reciprocatingly moves the zoom lens in the optical axis direction to be capable of being switched to two positions of a forward position and a backward position using the expansion and contraction of the shape memory alloy.
Note that examples of the forward position include a normal observation position at an equal magnification in the optical system and examples of the backward position include a near point magnifying observation position for performing a magnifying observation in the optical system.
Japanese Patent Application Laid-Open Publication No. 2000-221415 discloses a configuration of an operation switching mechanism in which a linear switch is used. The linear switch can reciprocatingly move a zoom lens frame, which holds a zoom lens in an insertion section of an endoscope, between a forward position and a backward position along a longitudinal direction of a wire substantially parallel to the optical axis direction and fix the zoom lens frame to be capable of being switched to the forward position and the backward position using two compression springs respectively wound in front and rear positions of the zoom lens frame around an outer circumference of a slide pin, which pierces through the zoom lens frame along an optical axis direction, and configured to respectively bias the zoom lens frame forward and backward in the optical axis direction and using the wire, which is a long member inserted through the insertion section of the endoscope, connected to the zoom lens frame, and towed and slacked using an operation member provided in an operation section of the endoscope.